Evaluating Expressions

1
Evaluating Expressions

• 3-1-1

2
Expressions

• An expression is variables and operations.
• Equations have equal signs and could be solved.
• An expression can be simplified and evaluated for
  given values.

3
x28

• To evaluate the expression x28 for x 5,
• Write the expression, replacing the variable
  with the known value.
• Simplify. Be careful with the order of
  operations.
• Notice the 5 is squared first. The result is
  added to 8.

4
Save a place for a number

• Putting parenthesis where the variable is to be
  filled in is a good idea.
• This isnt always necessary, but until you have
  had enough practice with negative numbers to know
  when parenthesis are needed and when they are
  not, always write them in.

5
Example x2 - y2

• Evaluate x2 - y2 for x -4 and y -5
• First, copy the pattern the expression makes.
  ( )2 ( )2
• Then fill in the spaces with the given values.
  (-4)2 (-5)2
• Simplify, exponents before subtraction.
• 16 25 -9

6
x2 - y2

• Work the same problem for x1 and y-4
• (1)2 (-4)2
• 1 16 -15

7
Mistakes

• Order of Operations
• Negative Rules
• Exponent rules

8
Example z-2xy2

• z-2xy2 for x-2, z-3, y- 4 (
  )-2( ) ( )2 (-3)-2(-2 )
  (- 4)2 (-3)-2(-2 )16
  (-3)416 1 16
  17

9
Example z-2xy2

• Try the same formula for x-1, y3 and z -2(
  )-2( ) ( )2